…This problem may occur because your computer is infected by the TrojanSpy:Win32/Banker Trojan horse program.

When this problem occurs, TrojanSpy:Win32/Banker takes the following actions:

• TrojanSpy:Win32/Banker sets the Internet Explorer home page to “about:blank.”

• TrojanSpy:Win32/Banker deletes all the files in the C:\Program Files\Microsoft AntiSpyware folder.
• TrojanSpy:Win32/Banker looks for Windows relating to Microsoft Windows AntiSpyware (Beta) and sends messages to these windows to close them.
• TrojanSpy:Win32/Banker shuts down processes that are associated with Microsoft Windows AntiSpyware (Beta).
• TrojanSpy:Win32/Banker tries to download and then run updates from a Web server.
• TrojanSpy:Win32/Banker tries to download and then run additional software from an FTP server.
• TrojanSpy:Win32/Banker prevents the user from accessing certain security Web sites.
• TrojanSpy:Win32/Banker removes the gcasServ registry entry from the following subkey:
  HKLM \ Software \ Microsoft \ Windows \ CurrentVersion \ Run

• TrojanSpy:Win32/Banker collects personal user information when a user visits online banking sites.

  [Continue reading Microsoft Knowledge Base article 894269: Microsoft Windows AntiSpyware (Beta) Unexpectedly Quits]